Goldfish are capable of making their own alcohol

Now we know how they cope with life in dreary fish bowls.

A wild-caught carp with goldfish coloration.
(Photo: George Chernilevsky/Wiki Commons)

When someone is a heavy drinker, we sometimes say that they "drink like a fish." Until now, we never knew just how apt that phrase truly was, at least as it pertains to goldfish and their carp relatives.

Scientists have found that your bored, lonely, yawning pet goldfish has a rather remarkable coping mechanism for those long weeks swimming in its murky fish bowl between cleanings: it makes its own alcohol and gets lit.

“The adaptation is very rare among animals,” said Michael Berenbrink, one of the researchers to make the discovery, to New Scientist.

It's such a rare trait, in fact, that no other vertebrate has been discovered with the ability. (And that's probably a good thing. Imagine what you would do with your own biological alcohol-production system!)

The adaptation didn't evolve as a mechanism for surviving fish bowl life, though that's a convenient bonus for pet goldfish. It's actually an adaptation for the harsh, oxygen-deprived conditions that wild carp often find themselves in, particularly when enduring frigid winters when the waters where they live freeze over.

Here's how they do it. When oxygen levels in water are deprived, carp activate a set of enzymes that anaerobically convert carbohydrates into alcohol. The process is similar to what happens in other animals-- humans included-- whereby carbohydrates are metabolized without oxygen. But when this process is activated in other animals, the end product is lactic acid instead of alcohol.

Lactic acid can be dangerous, which is why most animals can't survive long without oxygen. As this substance builds up in the body, it can cause that burning sensation in your muscles that you might experience when you overexert yourself. If it continues to build up, it will cause lactic acidosis, a condition that lowers the pH of tissues and causes all kinds of problems.

Alcohol is a much more friendly substance, despite its dizzying side effects. Not only is it easier to remove from the body, but it allows carp to potentially live for months without much oxygen. The only catch? When in this state, the fish develop blood alcohol levels of roughly 55 milligrams per 100 milliliters. To put that perspective, consider that in many places around the world, this would make it illegal for them to operate a vehicle.

So if your goldfish starts to swim a bit wobbly, it might be a signal that it's time to clean out its bowl. It will love you all the more for it, and that's not just because of the beer goggles.